“Pacing” leads as used in this description refers to leads for the delivery of low-energy pulses used for bradycardia or resynchronization therapies. It should be understood, however, that the invention also applies to cardioversion/defibrillation leads for delivering high energy electric shocks to the heart for terminating a tachyarrhythmia. Unless otherwise stated, the terms “stimulation lead (or electrode)” or “pacing/defibrillation lead (or electrode)” should be understood generally to mean and include any type of lead used for these purposes.
For endocardial stimulation of a left heart cavity, with the known techniques, it is necessary to achieve a puncture in the septal wall having a sufficient diameter to introduce a guide catheter. The guide catheter is used to establish communication between the right ventricle and the left ventricle through the wall of the septum in order to introduce into the latter a left endocardial pacing lead.
French application No. 10/53499 filed May 5, 2010 entitled “Endocardial Stimulation/Defibrillation System of the Left Ventricle” and its counterpart U.S. patent application Ser. No. 13/101,508, commonly assigned herewith to Sorin CRM S.A.S. of Clamart France, propose to remove the guide catheter associated with a lead through the septum, replacing this system by a conventional lead screwed onto the wall of the right ventricle in the septum, and extending the lead using a partially isolated transeptal microcable, that is pushed into the left ventricle until it comes into contact against a target site located in the left ventricle, for example, against the free wall of the latter.
In this case, the lead is used not only as a support for at least one sensing/pacing electrode, but also as a tool for guiding the microcable through the wall of the septum (to make a puncture allowing the microcable to pass through the wall) and beyond, into the left cavity.
The puncture can be performed by a simple mechanical push of the microcable if the rigidity of the microcable latter is sufficient. But the drilling in the interventricular septum is preferably assisted by a RF puncture technique, which involves applying a localized radio frequency energy (RF) produced by a suitable electronic generator to create a very small size opening in the tissue of the septal wall. The puncture is obtained by combining, on the one hand, the function obtained by the screw lead guiding the microcable with, on the other hand, the application of RF energy sufficient to allow the microcable to gradually penetrate through the septum and thus greatly minimize the axial force required to be transmitted at the proximal end of the microcable during this step. Indeed, in the absence of an applied RF energy, a microcable that is too thin could not penetrate the tissue and would buttress at the point of contact with the wall of the septum. Note also that the RF puncture technique advantageously provides a cauterizing of the traversed tissues, and thus prevents significant bleeding.
After drilling through the septum walls, the microcable is pushed beyond the septum, now crossed from one side to the other side, with a free part, the length of which can be up to about 120 mm, emerging in the interior volume of the left ventricle, beyond the intermediate portion enclosed in the septum. This emerging free part of the microcable is totally or partially bared and is an active portion coming into contact in one or more points with the wall of the left ventricle.
Once the system is thus implanted, the pulse generator is connected to the lead and to the microcable, with one terminal of the detection/stimulation circuit connected to the distal electrode of the lead (e.g., an electrode located in the right ventricle), and the other terminal of the same circuit connected to the free part of the active microcable (e.g., the free part localized in the left ventricle).
The application between these two electrodes of stimulation pulses produce an electric field encompassing a large part of the cardiac mass, thus allowing an effective stimulation of the left ventricle.
In one embodiment, the active part of the microcable emerging in the left ventricle has a much smaller length (about 10 mm or less) with a loop, so as to press the end of the microcable against the wall of the septum on the left ventricular (LV) side, thus defining a located stimulation site. The stimulation remains endocardial, but the mobility of the microcable and the surface thereof exposed to the arterial circulation are greatly reduced.
This lead configuration can also be applied to the case of a defibrillator. The free part of the active microcable is then connected to one terminal of the shock circuit of the generator, the other terminal of which is connected to: a right ventricular (RV) coil placed in the right ventricle, and/or a superior vena cava (SVC) coil placed in the superior vena cava near the right atrium, and/or to the housing of the generator, and/or the distal electrode of the lead if it has a sufficient area. Such a configuration advantageously allows covering a maximum heart mass, despite the relatively small electrode surface compared to a conventional shock electrode. In addition, the shock is applied between electrodes located on either side of the septum, the latter being “squeezed” in the electric field. This allows to further increase the effectiveness of defibrillation at constant energy, or to significantly reduce the energy of the delivered shock and therefore the associated pain, compared to a conventional configuration wherein the shock would be delivered between the housing of the generator and the RV and/or SVC coils.
Another application of the microcable described above is described in French application No. 10/59521 filed Nov. 19, 2010, for a “stimulation lead of a left cavity of the heart, implanted in the coronary system,” and corresponding U.S. patent Ser. No. 13/300,451 filed Nov. 19, 2011 (commonly assigned herewith to Sorin CRM S.A.S., of Clamart, France) which proposes to stimulate the left ventricle, to introduce the lead and the microcable in the coronary system rather than the cavity to be stimulated, the lead being extended by the free active part of the microcable with its stimulation electrodes applied against the wall of the epicardium at the level of the left heart cavity to be stimulated. The microcable overcomes the difficulties associated with the gradual reduction in diameter of the veins as the lead progresses in the selected coronary vein, and to multiple the points of contact with the epicardium, thus maximizing the effectiveness of the stimulation. This overcomes the difficulties encountered with conventional leads to find a satisfactory stimulation site, get a good electrical contact of the electrode against the tissue of the epicardium, and maintain this contact, despite the various changes or stresses over time.
The present invention relates to a specific stimulation system configuration (lead plus microcable) that is particularly well suited for the implementation of the techniques described in the aforementioned French patent application FR 10 53499 and its counterpart U.S. patent application Ser. No. 13/101,508, and FR 10 59521 and its counterpart U.S. patent application Ser. No. 13/300,451, the disclosures of which are incorporated herein by reference in their entirety.
It is desirable to provide a stimulation system configuration that:                Establishes a simple and reliable electrical connection between, on one hand, the distal or proximal electrode at the distal end of the lead and the microcable, and, on the other hand, the terminals for a standard connector (for example, an IS-1, IS-4 or DF-4 type connector) at the proximal end of the lead;        Adjusts accurately the length of microcable emerging in the left ventricle, for example, in a range of lengths from 5 mm (e.g., contact with the septum, left ventricle side) to 120 mm (e.g., contact with the left ventricle free wall), or in the coronary system;        Guarantees a guiding push on the microcable to puncture the wall of the septum during progression in the coronary system, avoiding any risk of kinking of the microcable when it is not wrapped by the lead;        Requires only simple and fast gestures already known by the surgeons, and not requiring specific training or any use of special tools;        Permits repositioning of the microcable during implantation of the stimulation system (possibly multiple times) and/or after surgery.        
The known devices proposed in the following publications have not met these requirements.
US Patent Publication No. 2001/0012958 A1 and 2010/0069983 A1 implement a classic probe (probe body forming the content) sliding in another conventional probe (probe body forming a container or guide) with a proximal side port through which emerges the probe body forming content.
US Patent Publication No. 2006/0064150 A1, for its part, offers a solution with two separate single-pole electrical outlets, with a single connector variation obtained by adding a parallel branch-type bypass.
US Patent Publication No. 2003/0023296 A1 has no telescopic function, even if it is otherwise an essential component of the system considered above.
None of these prior known publications disclose establishing an electrical connection between, on one hand, all distal electrodes and, on the other hand, a single proximal IS1 or IS4/DF4 type connector while avoiding the disadvantages of standard multi-line connection and providing a major advantage of simplicity of implementation on the operative field (e.g., no connection error to the head of the case, and a reduction of the volume of the system). In addition, these prior known publications either do not or hardly address the two critical issues of leakage and continuity of the electrical line, which are by nature a source of complication of a telescopic lead system. Moreover, the known solutions consisting of “stacking” conventional leads having to slide to (i.e. with a functional space between them) lead to larger sizes, which is inconsistent with the applications described above.